Re: [f2fs-dev] [PATCH v2] f2fs: fix hungtask when decompressed fail

[Eric Biggers <ebiggers@kernel.org>]

On Wed, Nov 02, 2022 at 11:06:17AM +0800, fengnan chang wrote:
> 
> 
> > 2022年11月2日 10:05，Eric Biggers <ebiggers@kernel.org> 写道：
> > 
> > On Wed, Jun 08, 2022 at 09:48:52PM +0800, Fengnan Chang wrote:
> >> When decompressed failed, f2fs_prepare_compress_overwrite will enter
> >> endless loop, may casue hungtask.
> >> 
> >> [   14.088665] F2FS-fs (nvme0n1): lz4 decompress failed, ret:-4155
> >> [   14.089851] F2FS-fs (nvme0n1): lz4 decompress failed, ret:-4155
> >> 
> >> Signed-off-by: Fengnan Chang <fengnanchang@gmail.com>
> > 
> > This commit message only explains the problem, not the solution.  It should
> > explain the solution too.
> > 
> > Also, if it's fixing a bug, it needs 'Fixes' and 'Cc stable' tags.
> 
> I’ll add more explanation and tags, thanks.
> 
> > 
> >> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> >> index 24824cd96f36..1764e3859262 100644
> >> --- a/fs/f2fs/compress.c
> >> +++ b/fs/f2fs/compress.c
> >> @@ -1060,7 +1060,7 @@ static int prepare_compress_overwrite(struct compress_ctx *cc,
> >> 	sector_t last_block_in_bio;
> >> 	unsigned fgp_flag = FGP_LOCK | FGP_WRITE | FGP_CREAT;
> >> 	pgoff_t start_idx = start_idx_of_cluster(cc);
> >> -	int i, ret;
> >> +	int i, ret, retry_count = 3;
> >> 
> >> retry:
> >> 	ret = f2fs_is_compressed_cluster(cc->inode, start_idx);
> >> @@ -1120,7 +1120,12 @@ static int prepare_compress_overwrite(struct compress_ctx *cc,
> >> 			f2fs_put_rpages(cc);
> >> 			f2fs_unlock_rpages(cc, i + 1);
> >> 			f2fs_destroy_compress_ctx(cc, true);
> >> -			goto retry;
> >> +			retry_count--;
> >> +			if (PageError(page) && !retry_count) {
> >> +				ret = -EIO;
> >> +				goto out;
> >> +			} else
> > 
> > What is the purpose of using PG_error here?
> 
> In this version, we set PG_error when compressed failed, so check PG_error here.
> Maybe we can remove PG_error in later?
> 

Read I/O errors can be detected via PG_uptodate not being set.  There shouldn't
be any need for PG_error here.

- Eric


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